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Discussion Starter · #1 ·
Having recently landed a 1980 CX500C with 17,800 original miles, I am extremely thankful for this forum. I'm good with everything else I've tackled so far, but this just plain baffles me totally:



Plastic floats, non-adjustable, without compressing the needle spring, read .750" (19.0mm) one side and >yikes< .820" (20.85mm) on the other side. a far cry from 15.5mm (.610" for those that don't measure bi-lingually). High reading means the fuel level is pretty horrifically low, right(?). I'm surprised it ran at all (had a broken throttle cable when I bought it, but I could rev it with a screwdriver). The bowls would overflow some when parked with gas left on, maybe that's why it ran decently? Anyway, I cleaned up everything and ordered new float needles.

I've swapped floats and old needles in various combinations back and forth between carbs and the crazy readings follow the float wherever it ends up.

It also seems bizarre to me that the old floats would wander off in the >low< direction (rather than bending 'up' with the usual forces at play over 31 years).

I'm in need of some sanity here, am I doing anything wrong? How do I get around this? The hairdryer bendy trick? If I get used floats, the situation could be worse (if that's possible), and NOS floats are like 50USD each...



please jump in SOON

thanks

mike
 

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Shep advocates heat to adjust the plastic floats and has had good success he sez. I don't think it's a common problem though, I have not experienced it in the many carbs I have had apart, so I would not fear much getting used floats if cheap enough.
 

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Welcome to the forum Mike. Nice to see another CX coming back to life.



The issue you're having with the floats isn't uncommon. Part of the problem is the new needles. They have always tended to be a bit too long, and will lower the floats. Were the stock needles a little better? If the spring tips and rubber tips are ok with the old needles, I would use those instead of the replacements.



Now, in the last year I have been raising the floats by filing the spring loaded tip down. It doesn't take much at all so go slowly. The tip is brass so it files or sands down pretty quickly. You'll have to check it several times so you don't go too far.



Another reason for using the OEM needles is that the spring loaded tip is longer than the aftermarket ones. It will leave you with enough cushion in the tip after filing them down.



I think the reason the floats tend to bend down after years is two fold. When a bike is in use all the time and has fuel in the bowls it keeps the floats raised up and suspended. The fuel also keeps the floats cooled down from engine a summer heat. When the bikes are stored and forgotten for years on end, usually outside, with empty bowls they hang against the stop tabs putting the weight of the floats on the thin arms. Without fuel in there to take off some of the heat from summers direct sun the plastic starts to heat up and lower the floats a little bit at a time. Over time they end up staying in that position.

Heating them up works ok, but it's a bit on the risky side. If you get them too hot they distort and become very brittle. It will work but filing the pin down is the safest way to go in my opinion.



You mentioned the overflows still leak a bit. You need to be sure the brass seats are clean and free of any nicks or corrosion. I use a small brass brush from a hobby supply store in a drill. Spinning it at high speed will clean and burnish the float seat so the needle sits properly. I have also used a small rubber type sanding cone from a jewelry supply shop to clean the seats up.





I hope this helps get the situation fixed for you. Good luck.



Also, could you take some time to finish you're profile and signature please? It helps us all know what you're working on and where you are in case you are close to another member that can help you out.
 

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Discussion Starter · #4 ·
thanks guys.

The new needles are in the mail, the old needles are where I got these readings (they didn't look bad, and cleaned up well). Burnishing the seats is on the list for this weekend, and micro-shortening the plunger sounds like a good option (after trying to heat bend the float arms).



-mike
 

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Discussion Starter · #6 ·
Problem (at least the float levels)SOLVED! The new OEM needles were the same length as what came out, but the spring pin end is slightly shorter. I put them in, and bingo! float levels are instantly within .5mm of target. A little flexing and we're on the money.

Side note, the "correct" needles have a sort of a 'star shaped' washer that it hangs on the floats with. the "wrong" ones have a round washer... so maybe they were the wrong ones?

Float seats are burnished (one was a little junky), and carbs are back together (except the bowl gaskets haven't arrived yet).

Tach cable & rad flush tomorrow!
 
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